Ilyas, Mohammad

This thesis addresses issues faced in the practical implementation of a wireless ad hoc network (WAHN) protocol for data transmission. This study focuses on: (1) Evaluating existing hardware and software options available for the WAHN implementation. (2) Appraising the issues faced while implementing a practical wireless ad hoc protocol. (3) Applying a set of MAC protocol specifications developed for a wireless ad hoc data network to a practical test network. Specific to the above topics of interest, the following research tasks are performed: (1) An elaborate survey and relevant discussions on wireless MAC protocols. (2) A comprehensive study comparing various wireless transceivers is performed. Range, data rate, frequency, interfacing method and cost are the factors compared. (3) A simple, low-cost and low baud-rate transceiver is modified with appropriate interface circuits to support wireless communications. A more advanced transceiver is also considered and used for the software foundation of a practical implementation of the ad hoc and MAC protocols. The studies enable assessing the problems faced during the implementation and suggest solutions to resolve these problems. Further areas for study are also discussed.

Asynchronous Transfer Mode (ATM) Networks are based on connections that are multiplexed dynamically on a single link. For satisfactory performance in an ATM network, congestion control is extremely necessary to guarantee the negotiated Quality of Service (QoS) for every connection. Traffic shaping is a congestion control mechanism that alters the traffic characteristics of a stream of cells on a connection to achieve better network efficiency by meeting the QoS objectives. We study a model for Traffic Shaping, Second Order Leaky Bucket, which consists of two leaky buckets to police the Sustained Cell Rate (SCR) and Burst Tolerance (BT) for each ATM connection. With this algorithm, ATM cells enter the first leaky bucket and the Cells conforming to the first leaky bucket enter the ATM network with Cell Loss Priority set to zero (CLP = 0). Any cell non-conforming to the first leaky bucket is sent to a second leaky bucket, and will be tagged CLP = 1 only if found to be non-conforming to the second leaky bucket. Cells conforming to the second leaky bucket are allowed to enter the ATM network with CLP = 0. We simulate the second-order leaky bucket for traffic shaping and show the effectiveness of second order leaky bucket in protecting the QoS experienced by connections passing through a common internodal link queue.

With the advent of cellular technology and portable computers we are on the verge of a new computing paradigm. This computing paradigm is now widely known as "mobile" or "nomadic" computing. Mobile systems frequently change their point of attachment to the network. Mobile computing systems also need to communicate with the existing pool of information and file servers. Mobility defies the very principles that the TCP/IP protocol suite is based on. We study the Internet Engineering Task Force (IETF) Mobile IPv4 protocol and find it to be a highly scale solution. We study some of the other proposed mobile IP solutions. We establish a criterion, call-to-mobility ratio, to compare various mobile IP schemes. Two hypothetical schemes, Static Update and Triangular Routing, are introduced solely for the purpose of comparing the performance of Mobile IPv4. In our simulation we concentrate on calculating the update costs and the routing costs for Triangular Routing, Static update and Mobile IPv4 schemes. The simulation program to simulate Triangular Routing, Static Update and Mobile IPv4 is written in C++. Minetsim, our simulation program is written using object-oriented analysis and design. Minetsim is used to obtain routing and update costs for Triangular Routing, Static Update and Mobile IPv4 schemes. Four different host configurations are simulated for travelling salesman and random motion mobility models.

Signal processing requires a steady flow of sampled data to be able to properly manipulate the signal to get the desired output. By using Asynchronous Transfer Mode (ATM) networks, it is possible to divide signal processing amongst a number of stations where each station can be specialized to a single function. Unfortunately, most commercially available ATM Network Interface Cards (NIC) only support message mode ATM Adaptation Layer 5 (AAL5) which is unsuitable to signal processing due to the delays of having to wait for an entire message to be formed prior to sending. It is shown that by using an ATM NIC using streaming mode AAL5, where cells are sent as soon as enough data to create an ATM cell of 48 bytes, leads to better quality signal processing. It is also shown that the message latency (time it takes for a message to traverse the network) is reduced by using streaming mode AAL5.

In order to effectively transport digital compressed video over Broadband Integrated Services Digital Networks (B-ISDN) with Asynchronous Transfer Mode (ATM), the characteristics of the video source traffic should be understood. The nature of the video traffic depends primarily on the source, the content of the video and the coding algorithm that removes redundancies for efficient transmission over networks. In this study, video conference data encoded using a subband coding scheme, Digital Video Compression System (DVCS), is analyzed to determine its characteristics. Several video traffic sources are multiplexed through an ATM network node with limited capacity and the performance of this environment is evaluated by using a simulation technique. The simulation results are presented for the performance measures for varying traffic and network conditions.

In this thesis we have proposed and analyzed a new architecture for high speed fiber optic LANs/MANs, called the Dual Bus R-Net. The scheme is based on a slotted unidirectional dual bus structure. It uses a reservation mechanism to generate slotted frames on each bus. Frames consist of a reservation slot and one or many information slots. Stations reserve slots by transmitting reservation requests on the bus carrying information in the opposite direction. The scheme has the advantage of superior channel utilization, bounded delay, fair access to all stations, dynamic bandwidth allocation to network users, and implementation simplicity. Extensive simulations have been carried out to verify the characteristics of the network. Simulation results reinforce the initial claims of the advantages offered by Dual Bus R-Net. Performance analysis is presented in terms of network delay and channel utilization. Simulation results are compared with similar results of X-Net, R-Net, DQDB, and Expressnet.

The primary emphasis of this thesis is to study the behavioral characteristics of Fiber Distributed Data Interface (FDDI) and Distributed Queue Dual Bus (DQDB) High Speed Local Area Networks (HSLANs). An FDDI architecture with passive interfaces is proposed to provide a reliable and efficient network topology. This network architecture outperforms the existing FDDI architecture with active interfaces in terms of small asynchronous packet delays and high asynchronous packet throughput. The design and implementation issues involved in the design of the hierarchical (multi-level) DQDB and FDDI networks are also presented. The hierarchical network architecture provides modularity and scalability with respect to speed and the number of users. Simulation models are developed for each of these network architectures to study their performance. Simulation results are presented in terms of medium access delay, throughput, and packet delays.

A Next Generation Computer Network Communications Architecture, CNCA, is developed in this thesis. Existing communication techniques and available networking technologies are explored. This provides the background information for the development of the architecture. Hardware, protocol, and interface requirements are addressed to provide a practical architecture for supporting high speed communications beyond current implementations. A reduction process is then performed to extract the optimal components for the CNCA platform. The resulting architecture describes a next generation communications device that is capable of very fast switching and fast processing of information. The architecture interfaces with existing products, and provides extensive flexibility. This protects existing equipment investments, and supports future enhancements.

An Advanced Intelligent Network (AIN) is described and its performance is evaluated in this thesis. First, the AIN architecture is presented. This is followed by the description of the operation and the creation of the telephone services in the AIN architecture. Finally, the AIN architecture is evaluated on the performance of the user-network interface and the network elements, and the expandability and cost effectiveness of the architecture. The result of the evaluation shows that the operation of the telephone services in the AIN architecture are acceptable according to the standards set by Bellcore. Therefore, the AIN architecture meets the objectives set by the telephone operating companies and provides a basis for faster development and deployment of new telephone services in a cost effective manner.

This thesis illustrates the design of non-proprietary and practical ISDN terminal equipment for basic access. Terminal compatibility with the AT&T 5ESS, Northern Telecom DMS100, and Siemens EWSD Class 5 switches is considered. General compliance is dictated by all applicable CCITT recommendations and BELLCORE technical references. A consolidation of the useful information in the CCITT and BELLCORE technical documents is provided from a design engineer's perspective. A practical, cost effective implementation is outlined and considerations for flexibility due to the changing requirements are explored. The objective is to specify simplified guidelines which can be followed to create generic ISDN terminal equipment which is non-proprietary and practical for ISDN subscribers today.